In the case where a resin composite including thermoplastic resin and carbon fibers is used for a body outer plate of a vehicle, for example, adhering is adopted as a joining method for joining the resin composites to each other.
The above resin composites are usually adhered with adhesive. However, a resin composite made of thermoplastic resin has no functional group contributing to enhancement of adhering strength. Thus, the resin composite without treatment exhibits low adhesion strength. It is therefore necessary to apply for example surface treatment to joining surfaces to be joined, leading to increases in time and cost. Furthermore, it also takes time to harden the adhesive.
As other welding (fusion-bonding) methods for resin composites, there are a hot-plate method and an ultrasonic wave vibration method. Either technique is hard to apply to large-sized components such as a body.
As the welding method for resin members, there has been known a technique for joining (fusion-bonding) a thermoplastic resin composition including a laser transmitting black coloring agent containing amine salt of anthraquinone dye or monoazo complex dye, from among the thermoplastic resin containing inorganic filler or reinforcer (Patent Literature 1).